Polaron in Bose-Einstein-Condensation System

We consider the motion of an impurity in a Bose-Einstein condensate system at T=0K with the contact interactions for boson-boson and boson-impurity. Under the forward-scattering approximation, we obtain a Frohlich-like Hamiltonian for this system, which means that a polaron can be formed. The effective mass, the phonon number and the energy to form a polaron are obtained. We also discuss the validity of the forward-scattering approximation for this system.